Manufacture of diarylamine derivatives



Patented July 7, 1936 UNITED fsr T PATENT OFFICE i 2,046,356 7 MANUFACTURE or DIARYLAMINE DERIVATIVES Max Wyler, Robert William Ker sey, and Harold Smith, Blackley, England, assignors to Imperial Chemical Industries Limited, a corporation of Great Britain No Drawing.

Application December 12, 1934;

Serial No. 757,234. In Great Britain December 'dlarylamine is converted tothe C-nitrosodiarylamine in one operation without isolation of any intermediate N-nitroso compound by treatin it with nitrous acid in methyl alcoholic hydrochloric acid.

In this specification diaryljnitrosamine means a diaryiamine in which theflhydrogen atom attached to the nitrogen atom 'is replaced by the nitroso group; diarylamine means two aryl radicals joined by an NH group. 1

We accomplish the objects of our invention by carrying out the operation throughout under anhydrous conditions. As solvent for the diarylamine we employ an anhydrous alcohol, for instance methyl alcohol, to which the hydrochloric acid required is added as an alcoholic solution. The requisite alkali-metal nitrite is added in dry, powdered form.

Our novel process has the advantage that it produces the nitroso-compound directly in high yield without the necessity of isolating any intermediate nitrosamines. This effect is particularly advantageous and surprising in the case of diarylamines of the general formula RNI-I-R, wherein R and R are aromatic hydrocarbons of the benzene or naphthalene series. Hitherto it has been believed that the nitroso compounds of these diarylamines could not be produced except by producing first and isolating the intermediate nitrosamine. phenylamine, 2-methyl-diphenylamine, and phenyl-a-naphthylamine are typical examples.

Our process is also applicable to cases wherein the hitherto known aqueous process could be worked in one step, for instance to the case of 4-acetyl-diphenylamine which is employed in the manufacture of 4-amino-4'-acetylaminodiphenylamine.

In carrying the invention into practical effect, the nitrous acid required may be provided by hydrochloric acid. The strength of the methyl alcoholic hydrochloric acid may vary, but for '5 Claims. (Cl. 260-69) best results should not be below 25%, and not over 40%. The required nitrosodiarylamine generally separates from the solution after formation, and with some nitrosodiarylamines it; is

convenient to add water for the purpose of '5 complete separation} V The following examples in which parts are by weight illustrate but do not limit the invention.

Example I 169 parts of diphenylamine are dissolved in 80 parts of methyl alcohol at- C. and the solution run into 800 parts of methyl alcoholic hydrochloric acid '(obtained by passing dry hydrogen chloride into methyl alcohol until the 15 solution contains 40% of its Weight of hydrogen chloride) with stirring, keeping the temperature below 30 C. After cooling the suspension to about 10 0, parts of powdered sodium nitrite are added and the mixture stirred for a short 20 time until 4-nitrosodiphenylamine formation is found to be complete as shown by the complete solubility of a test sample in dilute aqueous caustic soda. The mixture is diluted with twice its weightof water and the -m'tros odiphenyl- 25 amine is filtered off. The yield is excellent.

4 nitrosodiphenylamine gives a practically quantitative yield of l-aminodiphenylamine when reduced by known methods such as zinc and hydrochloric acid, sodium sulphide, glucose and 30 caustic soda solution, and the like.

Example II 22 parts of phenyl-a-naphthylamine are pasted with parts of methyl alcoholic hydro- 35 Example III 23 parts of p-acetylaminodiphenylamine (prepared by acetylating i-aminodiphenylamine) 45 are dissolved in 350 parts of methyl alcoholic hydrochloric acid (40% 1-101) 8 parts of sodium nitrite are stirred into the solution and the mixture stirred for 2-3 hours, at 25-30 C. with addition of a little further sodium nitrite, if a di- 50 luted sample does not show slight excess of hitrous acid on starch iodide paper. The mixture is cooled to 0 C. and the orange-yellow crystals of 4-nitroso-4-acetylaminodiphenylamine which separate are filtered off. 55

l V sodiphenylamine is preciptated from the solu- V tionby adding sodium bicarbonate.

This nitroso-derivative maybe separated-from alkaliinsoluble material by extracting with dilute caustic soda, filtering ofi'insoluble matter, and

re-precipitating the nitroso derivative from the" filtrate byacidifying with acetic acid or by adding sodium bicarbonate; V r Example IV' V 95 parts of 2-methyldiphenylamine are stirred with 1,000 parts of methyl alcoholic hydrochloric acid (40% HCl), and 40 parts of powdered sodium nitrite added The mixture is stirred for two hours, diluted with water,'neu-t tralizedlwith caustic soda and filtered from a little insoluble material. TheZ-meth'ylnitro- 7 If the nitroso bodies :are to be used {or the manufacture of the corresponding amines by reduction, this reduction may be; effected without isolating thenitroso compound from the aqueous caustic' soda solution mentioned above.

'It will be understood that the details of :our'

preferred processes as above-set forth may be variedwithin wide limitsQwithout departing 7 from the spirit of this invention! 'We claim:

with nitrous acid and then isomerizing the intermediately formed diaryl 'nitrosamine, the improvement which comprises effecting the nitrosation by the aid of ananhydrous alkali metal nitrite in anhydrous alcoholic-hydrochloric acid 35 medium.

' '2. Inthe process of producing a p-nit rosodiarylamine of the general formula (p) ON- R--NHR, wherein R and R are aryl hydro-- carbon radicals of the benzene or naphthalene 1. In'the process of producing apnitroso- 7 V diarylamine by reacting upon a diarylamine series, which process comprises reacting upon the correspondingdiarylamine with nitrous acid 7 and then isomerizing the intermediately formed diaryl nitrosamine, the improvement which comprisesefiecting the nitrosation by. the aid of an anhydrous alkali-metal nitrite ,7 in anhydrous i methyl-alcoholic-hydrochloric acid medium of between 25 and 40% strength based on the weight of the hydrochloric acid, whereby the nitrosation and isomeriza'tion proceed concurrently in the same' medium.

amine of the general formula (p) ON-'R- NH+R wherein Rand R. represent aromatic radicalsrof the benzene and naphthalene series, which comprises forming a solution of the cor- .3.I'I'he process of producing a p-nitroso-diaryl-J responding diarylamine in anhydrous alcoholic j hydrochloric acid, and adding an alkali-metal nitrite in 'dry form with stirringwhile keeping t soluble; in dilute aqueous caustic hol', containing-between 251and 40% by weight of hydrogen chloride, adding sodium nitrite powder and then diluting :the reaction; mass with water to precipitate theformed p-nitrosodiphenylamine. a 5. In the process of producing p-nitr'o'sodiphenylamine, the step which comprises reacting with anhydrous nitrous acid upon'diphenylamine. in an anhydrous alcoholic medium.

ROBERT WILLIAM KERSEY. t

SMITH. 

